This invention relates to the art of security devices and, more particularly, to an anti-theft device detachably mountable on a propeller blade of a propeller driven aircraft to preclude unauthorized operation thereof.
Small, propeller driven aircraft are often parked and left unattended outside in a remote area of a large airport, or outside at smaller, local airports, and in both cases there is very little traffic in the way of individuals in the area and, most often, no provision for security personnel to watch the unattended aircraft. Even if the owner of an aircraft normally parks the latter in a hanger, there are instances where the aircraft is temporarily parked outside the hanger and left unattended, or towed or taxied from the hanger to a maintenance area in which the aircraft is left unattended pending the inspection, performance of maintenance and the like by maintenance personnel. In these and other situations, such aircraft is subject to unauthorized use or operation as well as theft, especially at smaller airports where there is minimal air traffic and thus more than ample opportunity to steal or take a joy ride in the aircraft. Indeed, theft of aircraft is a growing problem.
Some smaller aircraft have key operated ignition systems in which wires can be readily crossed if necessary to enable operation of the engine of the aircraft. However, in connection with such small aircraft, owners often leave the key in place, especially when the aircraft has been parked in the maintenance area, whereby crossing of wires is not necessary to operate the aircraft. Moreover, some owners replace the key switch with a toggle switch, and many aircraft as manufactured do not have a key operated switch and are operable merely by actuating a toggle switch. While small aircraft are often tethered to the ground, such tethering is primarily for the purpose of maintaining the aircraft in place during high winds and is not for the purpose of deterring theft or unauthorized operation thereof. Indeed, such tethering arrangements include rope or other lines which are tied in place or provided with mechanical spring clasps or the like and, thus, are readily detached from the aircraft.
It has been proposed, as shown for example in U.S. Pat. No. 4,167,862 to Gould, to provide one blade of an airplane propeller with a removable device forming an eccentric weight so as to preclude operation and thus theft of the aircraft. However, the devices disclosed in the latter patent are not adjustable and are of a structure readily susceptible to destruction by a person intent upon stealing or otherwise using an airplane without authorization. Moreover, the structures are such that the device is readily displaceable relative to the propeller blade in a manner which can damage the blade and/or the shroud or spinner of the mounted end thereof. The inability to adjust the device relative to a given propeller blade promotes such potentially damaging displacement thereof relative to the blade and precludes selectivity with respect to positioning of the device along the blade. At the same time, use of the device is limited to propeller blades which can accommodate the fixed size of the device. This can restrict the location of the device to a point at which the eccentricity of the weight of the device is not sufficiently effective to preclude operation and thus theft of an aircraft. In particular with regard to the structure of the device, it is comprised of two semi-circular rings pivotally interconnected at one end by a pin and releasably connected at the opposite ends by a padlock, both of which connections are readily destructible by a thief.